Flat panel liquid crystal display devices typically include an array of picture elements ("pixels") arranged in multiple columns and rows. A liquid crystal display (LCD) includes a source of visible light that is reflected or projected toward the panel. Each pixel is addressable via drive circuitry that can selectively alter the molecular arrangement of the liquid crystal material associated with any pixel. The LCD is constructed so that alteration of the molecular arrangement of the liquid crystal material results in corresponding variations in the intensity of the light propagating through the associated pixel. The entire array of pixels is driven so that the light emanating from the panel defines an image.
Optical-type touch panels have been developed for use as input mechanisms for display devices. Generally, arrays of light emitters and detectors are mounted around the display screen of the display device to establish a plane of light beams passing across and near the display screen. One group of emitters is positioned across the top of the screen (in the "X" direction) and can be referred to as X-emitters. An aligned group of X-detectors is positioned across the bottom of the screen. Another group of emitters is positioned across one side of the screen (in the "Y" direction) and can be referred to as Y-emitters. An aligned group of Y-detectors is positioned across the other side of the screen.
Typically, the X-emitters are sequentially scanned from one side of the display screen to the other. The outputs of the X-detectors are monitored to detect an interruption in any X-emitter beam, the interruption being indicative of the presence of a finger or stylus near the display screen. Similarly, the Y-emitters are sequentially scanned from the top to the bottom of the display screen, and the outputs of the Y-detectors are monitored to detect an interruption in any Y-emitter beam.
Whenever a stylus is placed near the display screen, the location of the interrupted X-emitter beam and the interrupted Y-emitter beam is transmitted to the display device controller as an input representing the stylus X and Y position coordinates. The display is changed in a predetermined manner in response to that input.
Prior optical touch panels employed numerous discrete components (emitters and detectors) with associated mounting structures. Further, the resolution of prior optical touch panels is limited by the maximum number of emitters and detectors that can be mounted side-by-side across a display screen. Accordingly, the resolution of such a touch panel is generally lower than, for example, the number of pixels of the display device.